1. Field of the Invention
The present invention relates to an ink cartridge for supplying ink to an ink tank in an ink jet printer.
2. Description of the Prior Art
As shown in FIG. 6, a conventional ink cartridge is so constructed that the openings at both ends of a cartridge body 1 of an approximately cylindrical shape are respectively sealed with sealing films 2 and 3 to seal ink 4 in the cartridge body 1. To supply the ink 4 to an ink tank 5 in an ink jet printer, a sealing cap (not shown) is removed from a filler hole 6 of the ink tank 5, after which one end of the cartridge body 1 is inserted into the filler hole 6, causing the sealing film 2 on the one end of the cartridge body 1 to be torn open by a piercing projection 7 formed inside of the filler hole 6. Next, a piercing member 8 is fitted onto the other end of the cartridge body 1, and pushed downward till it stops, as shown by a dashed line in FIG. 6, at a stopping flange 9 formed around the outer circumferential surface of the cartridge body 1. This causes the sealing film 3 on the other end of the cartridge body 1 to be torn open by a seal opener 10 provided inside of the piercing member 8, allowing air to flow through an air inlet 11 formed in the piercing member 8 and through the torn sealing film 3 into the cartridge body 1, the air acting to push the ink 4 into the ink tank 5 through the torn sealing film 2.
However, since the construction of the abovementioned ink cartridge is such that the flowing of the ink 4 cannot be stopped in the middle once both the sealing films 2 and 3 are torn open, an erroneous operating procedure will cause the ink 4 to leak out onto adjacent areas of the ink jet printer. For example, after the one end of the cartridge body 1 has been inserted into the filler hole 6 of the ink tank 5, the cartridge body 1 may be drawn out of the filler hole 6 to see if the sealing film 2 on that end has properly been torn open. At this time, if the sealing film 3 on the other end is accidentally pierced by the piercing member 8, the ink 4 will be allowed to flow out. Furthermore, since an indicator is generally not provided an indicator for indicating the remaining level of the ink 4 in the ink tank 5, it is often the case with ink jet printers to fill the ink tank 5 up to the full ink level for fear that the ink might run out during the operation thereof. In this case, if the cartridge body 1 is inserted in the filler hole 6 even when the ink tank 5 is not at the ink empty level (the minimum ink level), oversupply of the ink 4 will occur with no means of stopping the ink 4 from leaking through the filler hole 6.